(a) Technical Field
The present disclosure relates to a method and an apparatus of controlling a creep torque for a vehicle including a driving motor, and more particularly, to a method and an apparatus of controlling a creep torque for a vehicle including a driving motor capable of outputting a creep torque suitable for a driving tendency of a driver.
(b) Description of the Related Art
Generally, hybrid electric vehicles, electric vehicles, and fuel cell vehicles, which are considered environmentally-friendly vehicles, are driven by a driving motor obtaining a rotating force via electric energy. In particular, a hybrid electric vehicle efficiently combines the power of an internal combustion engine with the power of the driving motor.
A hybrid electric vehicle generally uses an engine, a driving motor, an engine clutch controlling power between the engine and the driving motor, a transmission, a differential gear apparatus, a battery, an integrated starter and generator (ISG) to start the engine or generate power by an output of the engine, and a wheel. The integrated starter & generator may be referred to as a hybrid starter & generator (HSG). The hybrid electric vehicle provides various driving modes, such as i) an electric vehicle (EV) mode which uses only the power of the driving motor by coupling or releasing the engine clutch depending on the driver's acceleration and deceleration, a vehicle speed, a state of charge (SOC) of a battery, and the like, ii) a hybrid electric vehicle (HEV) mode which uses a torque of the driving motor as auxiliary power while using a torque of the engine as main power, and iii) a regenerative braking mode which recovers braking and inertial energy generated when the vehicle is driven by braking or inertia by power generation of the driving motor and which charges (i.e., stores) the recovered braking and inertial energy in a battery. The hybrid electric vehicle also use mechanical energy of the engine and electrical energy of the battery together, use an optimal operational range of the engine and the driving motor, and recover energy at the time of braking to be able to improve fuel efficiency and use efficient energy.
Furthermore, with respect to the hybrid electric vehicle, creep torque control process refers to a control of the driving motor which is performed in a creep driving state (i.e., state in which an accelerator pedal is not pressed). According to existing conventional creep torque control processes, the creep torque is controlled based on a predetermined creep torque map independent of the driver's tendency.
In this regard, FIG. 7 is a diagram illustrating the existing creep torque map. As shown in FIG. 7, the creep based depending on the vehicle speed is set in the creep torque map so that the hybrid electric vehicle may perform creep driving. The existing creep torque map is fixed.
Acceleration of the hybrid electric vehicle while creep driving is changed depending on loads (e.g., gradient of a road, weight of the hybrid electric vehicle, and the like) applied to the hybrid electric vehicle. When the hybrid electric vehicle is going downhill, the vehicle speed reaches a target vehicle speed (i.e., a driver-desired vehicle speed) relatively quickly, and thus, the driver quickly steps on the brake. Conversely, when the hybrid electric vehicle is going uphill, the vehicle speed reaches the target vehicle speed relatively slowly, and thus, the driver either steps on the brake slowly or does not step on the brake at all.
In particular, when the driver frequently steps on the brake while creep driving, it may be determined that unwanted extra creep torque is being generated. In this case, only a high torque region (R) of the creep torque map is used, and the extra creep torque is lost as heat energy through operation of the brake, thereby deteriorating fuel efficiency. This problem also occurs while the hybrid electric vehicle is driving on a congested road (e.g., in traffic) or is parked.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore may contain information that does not form the related art that is already known in this country to a person of ordinary skill in the art.